1. Field of the Invention
The present invention relates to a method of forming a resist pattern which can easily and efficiently form a smoothed resist pattern in which a surface, at least wall surfaces, thereof is reduced its surface roughness and then smoothed. The present invention also relates to a method of manufacturing a semiconductor device which can efficiently manufacture a high-performance semiconductor device by carrying out a highly detailed patterning using a smoothed resist pattern formed by the aforementioned method of forming a resist pattern.
2. Description of the Related Art
In forming an extremely fine pattern on a semiconductor integrated circuit, a lithography is an essential technique. The lithography is such technique that a resist film is applied on a substrate forming a thin film and is selectively exposed and developed so as to form a resist pattern, and dry etching is carried out using the resist pattern as a mask, and thereafter, the resist pattern is removed. Conventionally, ultraviolet radiation is used as a light source for the selective exposure in the lithography. However, as patterns have become increasingly finer, in recent years, an ArF Excimer laser, which has shorter wavelengths than ultraviolet radiation, has more commonly used as the light source for the selective exposure.
In exposure techniques using the ArF Excier laser as the light source for selective exposure, however, a problem arises in that it is not possible to use resist materials which the light source for patterning has longer wavelength than the ArF Excimer laser. Namely, such resist materials overly absorb the ArF Excimer laser and the light cannot be transmitted through these resist materials, such resist materials therefore do not function as resists when the ArF Excimer laser is utilized as the exposure light source. Accordingly, resist materials of novel compositions, mainly novel materials of adamantane and COMA, have been improved and used when an ArF Excimer laser is used in selective exposure. These novel materials have sufficient transmittance with respect to ArF Excimer laser light (whose wavelength is 193 nm).
When such novel materials are used, the patterning can be carried out using the ArF Excimer laser. However, a problem still arises in that the opening dimensions at the wall surface (edge portions) of the formed resist pattern, so-called edge roughness, become considerably varied. Namely, although pattern sizes have become more and more fine recently, the finer the pattern size becomes, the greater the proportion, in the entire resist extraction pattern, of roughness at the wall surfaces of the resist pattern. As a result, a problem arisen in that the opening dimensions become largely varied.
Here, methods have been proposed for obtaining resist patterns having reduced roughness at the surface thereof and a smoothed surface, by improving resist materials having small edge roughness or by making the resist pattern re-flow by heating after it has been formed. However, with such methods, there is the problem that deformation of the resist pattern and variations in the size of the resist pattern before and after the surface is smoothed are large.